Fermented Foods and Bone Health – the FERMBONE Study
Can plant-based fermented foods influence gut microbiota, nutrient bioavailability, and bone metabolism? Using the international VEGANScreener dataset and a new RCT, we are investigating these open questions.
Factsheet
- Schools involved School of Health Professions
- Institute(s) Nutrition and Dietetics
- Funding organisation SNSF
- Duration (planned) 01.10.2025 - 30.09.2028
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Head of project
Prof. Dr. Leonie-Helen Bogl
Isabelle Herter
Monika Cahova - Project staff Natalie Sara Bez
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Partner
Nicholas Bokulich, ETH Zürich Department of Health Sciences and Technology
Anna Greppi, Laboratory of Food Systems Biotechn. Instit. of Food, Nutrition a. Health ETH Zurich
Marek Kuzma, Institute of Microbiology of the CAS, Czech Republic
Markus Schuppler, Laboratory of Food Syst. Biotechn. Instit. of Food, Nutrition a. Health ETH Zurich - Keywords Vegan diet, Fermented foods, Gut microbiota, Bone metabolism, Nutrient bioavailability, Bone turnover markers (CTX, P1NP)
Situation
Plant-based diets have become increasingly popular, with vegan diets representing the most restrictive form. While linked to sustainability and reduced chronic disease risk, these diets may lack key micronutrients and contain absorption inhibitors. Bone health is a concern: studies consistently show lower BMD, higher bone turnover, and increased fracture risk in vegans, especially women. Findings from EPIC-Oxford and Adventist Health Study 2 suggest that supplementation may reduce some risks, yet the mechanisms remain unclear. Growing evidence highlights the gut–bone axis, indicating that gut microbiota and their metabolites—particularly short-chain fatty acids—can affect bone metabolism by influencing nutrient absorption, inflammation, and osteoclast activity. Fermented foods, rich in live microbes and microbial metabolites, can beneficially shape the gut microbiota and may improve nutrient bioavailability by reducing inhibitors such as phytates and oxalates. While fermented dairy products have shown positive effects on bone markers and BMD, comparable evidence for plant-based fermented foods is lacking. To date, no randomized controlled trials have examined how fermented plant-based foods impact gut microbiota, bone turnover markers, or bone health. This evidence gap highlights the need for systematic research to understand their potential role in supporting bone metabolism, particularly among vegans.
Course of action
This study aims to clarify how plant-based fermented foods influence gut microbiota, nutrient bioavailability, and bone metabolism in vegan populations. The primary objective is to test whether a 12-week intervention with selected plant-based fermented foods improves bone health in premenopausal vegan women. We expect beneficial modulation of gut microbiota and favorable changes in bone turnover markers—reduced CTX and increased P1NP. Secondary aims include assessing whether long-term adherence to a vegan diet increases bone resorption independent of calcium intake; characterizing microbial viability and metabolite production in plant-based fermented foods; determining whether fermentation enhances bioaccessibility and bioavailability of key micronutrients compared with non-fermented foods; and comparing gut microbial metabolite profiles derived from fermented versus non-fermented foods. Our approach integrates cross-sectional analyses across five European countries and an RCT in Switzerland and the Czech Republic. This multinational design increases generalizability by capturing diverse dietary patterns, genetic backgrounds, and environmental exposures. Comparative analyses enable identification of factors shaping bone health and microbiota profiles. Larger combined samples strengthen statistical power, while institutional collaboration ensures methodological rigor and efficient resource use.
Looking ahead
In WP1, we analyse data from the VEGANScreener study to understand how bone turnover markers (CTX, P1NP) and bone mineral density differ between vegans and omnivores across five countries. We also examine how the consumption of fermented foods and overall dietary patterns relate to these markers. In WP2, we analyse plant-based fermented foods by identifying their microbial composition, the metabolites they produce, and their levels of key minerals and absorption inhibitors. This involves microbiological culturing, DNA-based methods, and chemical and mineral analyses. In WP3, we investigate in the laboratory how well minerals from fermented foods become available for absorption and how these foods influence the gut microbiota. We use an in vitro digestion model, test mineral uptake in Caco-2 cells, and assess the response of vegan gut microbiota in a cultivation system, including the resulting metabolites. In WP4, we conduct a randomized crossover trial with 40 premenopausal vegan women in Switzerland and the Czech Republic. Participants consume either fermented or non-fermented plant-based foods in two 12-week phases. We collect data on bone turnover markers, gut microbiota, inflammatory markers, and detailed dietary intake.
